With the increasing demand for electronic devices to have reduced current consumption, and to further avoid excessive use of off-chip components, there has been an increasing trend for electronic devices to perform an increased amount of processing in the digital domain. Electronic devices for generating digital signals, representative of amplitude modulated and encoded analogue signals, are well known. Consequently, there has been an increasing demand for high-resolution, low-power, and inexpensive analogue-to-digital converter.
One group of such electronic devices includes rotary transducers that provide instantaneous information regarding angular position about an axis, and means for rendering that information in digital form. Such transducers include resolvers, i.e. electromagnetically-operated sensing analogue devices, which are typically combined with further electronic components to provide a digital output representative of a measured mechanical angular position.
Product packaging plants and stamping press lines are ideal examples of where you might find resolver based systems in operation. In typical applications, the resolver sensor feeds rotary position data to a decoder stationed in a Programmable Logic Controller (PLC) that interprets this information and executes commands based on the machine's position. Thus, resolvers are widely used and particularly their role in the world of automation is unparalleled.
A resolver typically comprises a rotor that generally has an input or excitation winding and a stator having a pair of output windings. The excitation winding is driven by a sine wave reference. As the rotor turns, the coupling relationship from the rotor to the stator changes correspondingly with shaft angle. In particular, the amplitudes of the voltages of the stator windings ideally respectively vary as the sine and the cosine of the shaft angle.
The detailed output voltage of each output winding can be expressed mathematically by a first term that is in-phase with the carrier excitation and independent of the angular velocity, and a second term that is exactly in-quadrature with the carrier excitation and depends linearly on the velocity of the rotor. Therefore, synchronous demodulation of the sensor (resolver) output will yield signals representative of the sine and cosine of the shaft angle, independently of velocity. As the sine and cosine components of an angle uniquely define that angle, then the resolver output can be decoded to measure the resolver mechanical angle, independently of resolver velocity.
The majority of resolvers generate one or several sine and cosine cycles per rotor turn—the number of cycles reflects the number of pole pairs of the resolver. A maximum of 3-pole pairs resolvers are typically used in industrial, appliance and automotive applications yielding maximum of three sine and cosine cycles per rotor turn—the more cycles per rotor turn the better accuracy of the final angular position and speed measurement.
Nowadays developers of modern systems often require more added value and accuracy, in less space, in order to address specific needs of their designs. Due to this fact, recently introduced Sin-Cos sensors based on the magneto-resistance, optical and inductive principles are more advanced and capable of generating higher numbers of sine and cosine cycles per rotor turn. This yields higher accuracy of the angular position and speed measurement.
Often, these modern Sin-Cos sensors are sold as application specific integrated circuits, as shown in the arrangement 100 of FIG. 1. Here, a Sin-Cos sensor 105 outputs both a sine waveform 110 and a cosine waveform 115 directly to the dedicated processing circuit (ASIC) 120. The processing ASIC 120 then interprets this data to provide outputs relating to speed 125 and position 130 of the rotor windings to a digital signal controller (DSC) or microcontroller 135.
However, in a number of applications, this requirement to additionally integrate a dedicated Sin-Cos sensor processing ASIC 120 on the printed circuit board, solely to deal with accurately determining Sin-Cos output signals, significantly increases design costs, which naturally provide an opportunity for novel and low-cost Sin-Cos sensor signal processing solutions.
General angle tracking observer algorithms are known. Such algorithms are only used in cases having up to several sine and cosine cycles per rotor turn. Furthermore, processing of high numbers of sine and cosine cycles, per rotor revolution, inherently require a shortened period for an angle observer calculation. This significantly increases the processing load in extracting data relating to the position, speed and number of revolutions of the rotor windings, from signals extracted from the Sin-Cos sensor.
Thus, in summary, known hardware solutions for extracting information from Sin-Cos sensors are predominantly ASIC-based. Hence, these solutions are generally expensive and fail to provide customers with an adequate level of flexibility and/or estimation accuracy. In contrast, existing software solutions fail to provide accurate estimations and/or require huge computational power to perform accurate estimation.
The existing software solutions are based on reading and processing tenths of sine and cosine samples per one cycle (rotor turn). Utilizing existing software solutions for processing modern and highly integrated Sin-Cos sensors, distinguished by high number of sine and cosine cycles generated per rotor turn, naturally brings increasing demand for processing power. The processing power demand grows linearly with a number of sine and cosine cycles per rotor turn. Modern Sin-Cos sensors generate from 32 up to 1024 sine and cosine cycles per rotor turn, thus, effectively eliminating usage of standard software methods (drivers) for processing their sine and cosine signals.
US20050132802 A1, describes an angle computation method and apparatus for variable reluctance resolver, MINEBEA CO., LTD. US20040210416 A1, describes a measuring system for processing angular and linear measured values. U.S. Pat. No. 6,754,610 B2, describes digital signal processing of resolver rotor angle signals.
The above solutions are based on processing sensor analog sine and cosine signals. Therefore, their processing demand rises linearly with increasing number of sine and cosine cycles per rotor turn, which results in their teaching being less applicable for present day needs.
Thus, a need exists for an improved mechanism to process Sin-Cos data from a Sin-Cos sensor and method of operation therefor.